
arXiv: math/9803098
It is well known that any nonsingular M-matrix admits an LU factorization into M-matrices (with L and U lower and upper triangular respectively) and any singular M-matrix is permutation similar to an M-matrix which admits an LU factorization into M-matrices. Varga and Cai establish necessary and sufficient conditions for a singular M-matrix (without permutation) to allow an LU factorization with L nonsingular. We generalize these results in two directions. First, we find necessary and sufficient conditions for the existence of an LU factorization of a singular M-matrix where L and U are both permitted to be singular. Second, we establish the minimal block structure that a block LU factorization of a singular M-matrix can have when L and U are M-matrices.
Rings and Algebras (math.RA), LU factorization, FOS: Mathematics, Mathematics - Combinatorics, Mathematics - Rings and Algebras, Combinatorics (math.CO), M-matrix, Direct numerical methods for linear systems and matrix inversion, block matrix, Factorization of matrices
Rings and Algebras (math.RA), LU factorization, FOS: Mathematics, Mathematics - Combinatorics, Mathematics - Rings and Algebras, Combinatorics (math.CO), M-matrix, Direct numerical methods for linear systems and matrix inversion, block matrix, Factorization of matrices
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